Ground the OAuth metadata doc types in the SDK's (#524)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: alistair3149

src/auth/authorizationServer/asMetadata.ts

@@ -1,18 +1,22 @@
+import type { OAuthMetadata } from '@modelcontextprotocol/server';
 import type { ProxyConfig } from './proxyConfig.ts';
 
-export interface AsMetadataDoc {
-	issuer: string;
-	authorization_endpoint: string;
-	token_endpoint: string;
-	registration_endpoint: string;
-	response_types_supported: string[];
-	grant_types_supported: string[];
-	code_challenge_methods_supported: string[];
-	token_endpoint_auth_methods_supported: string[];
-	authorization_response_iss_parameter_supported: boolean;
-	client_id_metadata_document_supported: boolean;
-	scopes_supported?: string[];
-}
+// The SDK's RFC 8414 document type, narrowed to the fields this proxy always
+// emits: the spec and its registry extensions make them optional, but clients
+// pick a compatible flow from these advertisements (grant types, auth
+// methods, PKCE, DCR, iss, CIMD).
+export type AsMetadataDoc = OAuthMetadata &
+	Required<
+		Pick<
+			OAuthMetadata,
+			| 'registration_endpoint'
+			| 'grant_types_supported'
+			| 'code_challenge_methods_supported'
+			| 'token_endpoint_auth_methods_supported'
+			| 'authorization_response_iss_parameter_supported'
+			| 'client_id_metadata_document_supported'
+		>
+	>;
 
 /**
  * Builds the RFC 8414 authorization-server metadata document advertising this

src/auth/oauthFlow.ts

@@ -2,6 +2,10 @@
 
 const TIMEOUT_MS = 5000;
 
+// Deliberately not the SDK's OAuthTokens, which requires token_type and makes
+// expires_in optional — the inverse of what post() enforces. expires_in must
+// be present because token stores schedule refresh from it; token_type may be
+// absent in MediaWiki responses.
 export interface TokenResponse {
 	access_token: string;
 	refresh_token?: string;

src/auth/protectedResource.ts

@@ -1,4 +1,5 @@
 // src/auth/protectedResource.ts
+import type { OAuthProtectedResourceMetadata } from '@modelcontextprotocol/server';
 import type { UpstreamAsMetadata } from './metadata.ts';
 
 const RESOURCE_DOCUMENTATION =
@@ -21,13 +22,13 @@ export interface ProtectedResourceInput {
 	authorizationServers: readonly string[];
 }
 
-export interface ProtectedResourceDoc {
-	resource: string;
-	authorization_servers: string[];
-	bearer_methods_supported: string[];
-	scopes_supported?: string[];
-	resource_documentation?: string;
-}
+// The SDK's RFC 9728 document type, narrowed to the fields this server always
+// emits: RFC 9728 makes them optional, but a doc without an authorization
+// server would leave a client nowhere to sign in.
+export type ProtectedResourceDoc = OAuthProtectedResourceMetadata &
+	Required<
+		Pick<OAuthProtectedResourceMetadata, 'authorization_servers' | 'bearer_methods_supported'>
+	>;
 
 function anyWikiHasOAuth(wikis: Record<string, { oauth2ClientId?: string | null }>): boolean {
 	return Object.values(wikis).some(